He mentions this is from a podcast. Anybody know what podcast? It seems like something I might like to listen to.
The compiler is your best friend
31–40 of 149 posts
Re: The compiler is your best friend
#32Earlier quoted context omitted.
Do you not make such a tacit assumption every time you index into an array (which in almost all languages throws an exception on bounds failure)? You always have to make assumptions that things stay consistent from one statement to the next, at least locally. Unless you use formal verification, but hardly anyone has the time and resources for that.
If such an error happens, that would be a compiler bug. Why? Because I usually do checks against the length of the array or have it done as part of the standard functions like `map`. I don't write such assumptions unless I'm really sure about the statements, and even then I don't.
> or have it done as part of the standard functions like `map`.
Which are all well and good when they are applicable, which is not always 100% of the time.
> Because I usually do checks against the length of the array
And what do you have your code do if such "checks" fail? Throw an assertion error? Which is my whole point, I'm advocating in favor of sanity-check exceptions.
Or does calling them "checks" instead of "assumptions" magically make them less brittle from surrounding code changes?
Re: The compiler is your best friend
#33Earlier quoted context omitted.
> A comment "this CANNOT happen" has no value on itself. I think it does have some value: it makes clear an assumption the programmer made. I always appreciate it when I encounter comments that clarify assumptions made.
But if you spell that `assert(false)` instead of as a comment, the intent is equally clear, but the behavior when you're wrong is well-defined.
At least on iOS, asserts become no-ops on release builds
Re: The compiler is your best friend
#34This was a great breakdown and very well written. I think you made one of the better arguments for rust Ive read on the internet but you also made sure to acknowledge that large code bases are just a different beast all together. Personally I will say that AI has made making code proofs or "formal verification" more accessible. Actually writing a proof for your code or code verification is very hard to do for most programmers which is why it is not done by most programmers, but AI is making it accessible and with formal verification of code you prevent so many problems. It will be interesting to see where programming and compliers go when "formal verification" becomes normal.
Re: The compiler is your best friend
#35Earlier quoted context omitted.
Worse: You may created the proof. You may have linked to the proof. But if anyone has touched any of the code involved since then, it still has no value unless someone has re-done the proof and linked that. (Worse, it has negative value, because it can mislead.)
Not really. A quick git blame (or alternative) will give you the required information about the validity of such proof.
You must have some git plugin I haven’t heard about.
Re: The compiler is your best friend
#36Earlier quoted context omitted.
Do you not make such a tacit assumption every time you index into an array (which in almost all languages throws an exception on bounds failure)? You always have to make assumptions that things stay consistent from one statement to the next, at least locally. Unless you use formal verification, but hardly anyone has the time and resources for that.
If such an error happens, that would be a compiler bug. Why? Because I usually do checks against the length of the array or have it done as part of the standard functions like `map`. I don't write such assumptions unless I'm really sure about the statements, and even then I don't.
Do you really have code that's
if array.Len > 2 { X = Y[1] }
For every CRUD to that array?
That seems... not ideal
Re: The compiler is your best friend
#37I really like modern Swift. It makes a lot of what this author is complaining about, impossible. The worst file I ever inherited to work on was the ObjC class for Instagram’s User Profile page. It looked like it’d been written by a JavaScript fan. There were no types in the whole file, everything was an ‘id’ (aka void*) and there were ‘isKindOfClass’ and null checks all over the place. I wanted to quit when I saw it.…
Modern swift makes this technically possible but so cluttered that it's effectively impossible, especially compared with typescript.
Swift distinguishes between inclusive and exclusive / exhaustive unions with enum vs protocols and provides no easy or simple way to bridge between the two. If you want to define something that typescript provides as easy as the vertical bar, you have to write an enum definition, a protocol bridge with a type identifier, a necessarily unchecked cast back (even if you can logically prove that the type enum has a 1:1 mapping), and loads of unnecessary forwarding code. You can try and elide some of it with (iirc, its been a couple years) @dynamicMemberLookup, but the compiler often chokes on this, it kills autocomplete, and it explodes compile times because Swift's type checker degrades to exponential far more frequently than other languages, especially when used in practice, such as in SwiftUI.
Re: The compiler is your best friend
#38> How many times did you leave a comment on some branch of code stating "this CANNOT happen" and thrown an exception? Did you ever find yourself surprised when eventually it did happen? I know I did, since then I at least add some logs even if I think I'm sure that it really cannot happen. I'm not sure what the author expects the program to do when there's an internal logic error that has no known cause and no defini…
Ideally, if you can convince yourself something cannot happen, you can also convince the compiler, and get rid of the branch entirely by expressing the predicate as part of the type (or a function on the type, etc.)
Language support for that varies. Rust is great, but not perfect. Typescript is surprisingly good in many cases. Enums and algebraic type systems are your friend. It'll never be 100% but it sure helps fill a lot of holes in the swiss cheese.
Because there's no such thing as a purely internal error in a well-constructed program. Every "logic error" has to bottom out in data from outside the code eventually-- otherwise it could be refactored to be static. Client input is wrong? Error the request! Config doesn't parse? Better specify defaults! Network call fails? Yeah, you should have a plan for that.
Re: The compiler is your best friend
#39Earlier quoted context omitted.
But if you spell that `assert(false)` instead of as a comment, the intent is equally clear, but the behavior when you're wrong is well-defined.
At least on iOS, asserts become no-ops on release builds
You can (and probably should) undef NDEBUG even for release builds.
Re: The compiler is your best friend
#40I really like modern Swift. It makes a lot of what this author is complaining about, impossible. The worst file I ever inherited to work on was the ObjC class for Instagram’s User Profile page. It looked like it’d been written by a JavaScript fan. There were no types in the whole file, everything was an ‘id’ (aka void*) and there were ‘isKindOfClass’ and null checks all over the place. I wanted to quit when I saw it.…
Modern swift makes this technically possible but so cluttered that it's effectively impossible, especially compared with typescript. Swift distinguishes between inclusive and exclusive / exhaustive unions with enum vs protocols and provides no easy or simple way to bridge between the two. If you want to define something that typescript provides as easy as the vertical bar, you have to write an enum definition, a prot…
I think you’re conflating 'conciseness' with 'correctness.' The 'clutter' you're describing in Swift like, having to explicitly define an Enum instead of using a vertical bar |, is exactly what makes it more robust than TS for large-scale systems.
In TypeScript a union like string | number is structural and convenient, but it lacks semantic meaning. In Swift, by defining an Enum, you give those states a name and a purpose. This forces you to handle cases exhaustively and intentionally. When you're dealing with a massive codebase 'easy' type bridging is often how you end up back in 'id' or 'any' hell. Swift’s compiler yelling at you is usually it trying to tell you that your logic is too ambiguous to be safely compiled which, in a safety first language, is the compiler doing its job.